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    Facilitação indireta entre plantas em uma restinga arbustiva
    (Universidade Federal de São Paulo (UNIFESP), 2020-05-26) Ribeiro, Renata Marques [UNIFESP]; Castanho, Camila de Toledo [UNIFESP]; Universidade Federal de São Paulo
    Evidence denote that positive interactions between plants (i.e. facilitation) are more frequent in environments under severe environmental conditions. In addition to the benefits resulting from improved environmental conditions and availability of resources, it is possible that the facilitation by nurse plants will be even more intense if indirect facilitation also occurs via suppression of competing species. This study tested the existence of indirect facilitation of a nurse species mediated by the suppression of supposedly competing herbs. Therefore, we tested if: i) the nurse-plant Guapira opposita has a direct negative effect on the performance of herbaceous plants; ii) herbaceous plants have a direct negative effect on the performance of the early stages of life of the woody species Ternstroemia brasiliensis and iii) G. opposita facilitates indirectly T. brasiliensis. We implement this study in the shrub restinga located in the south of Ilha do Cardoso State Park, Cananéia, SP. To test the first hypothesis, we observed patterns association between G. opposita and herbaceous in the whole community. We expected to find less herbaceous richness and abundance under G. opposita than in open microsites. Additionally, to test hypotheses 1-3, we manipulated the presence of G. opposita and the Andropogon sp. herbaceous. In a factorial design with transplantation and monitoring T. brasiliensis performance about 600 seedlings and 600 seeds. We also tested how the presence of the nurse-plant and herbaceous changes different environmental conditions. Regarding the first hypothesis, the G. opposita effects on herbaceous diversified from negative to neutral depending on the performance measure and the functional type. G. opposita decreased the richness (p=0,03) and the abundance (p=0,003) of herbaceous grasses. However, in particular, G. opposita did not affect any growth indicator of the grass Andropogon sp., a species among the most abundant in the study area. In addition, G. opposita decreased the richness (p=0,03) but did not affect the abundance (p=0,70) of forbs species. Such negative effects may be related to G. opposita canopy shade on herbaceous plants, the effects of which are more intense in grasses that have a C4 photosynthetic route and, therefore, greater light demand. Different than expected by the second hypothesis, the Andropogon sp. effects fluctuated from neutral to positive depending on the target plant performance measure. Andropogon sp. increased the seed germination (p=0,03) but did not affect seedling survival after 11 months of experiment (p=0,63). The herbaceous also increased the seedlings height growth (p=0,01), but did not affect the other growth indicators. However, the positive effects of Andropogon sp. on T. brasiliensis do not seem to be related to soil temperature, humidity or nitrogen availability, since the presence of the herbaceous did not alter these environmental variables. Whereby the evidence denote that G. opposita does not affect the Andropogon sp. performance, and the herb, in turn, seems act as a facilitating plant for T. brasiliensis, the indirect interaction of G. opposita on T. brasiliensis is neutral, and not positive as expected. Thus, the positive interactions of the nurseplant on T. brasiliensis seems to be restricted to direct interactions. In summary, the results suggest that the presence of facilitating individuals, both woody and herbaceous, are important for the woody plants performance in the early life stages which is very susceptible to the severe environmental conditions of coastal dunes.